It’s fitting that Mitt Romney’s choice of Paul Ryan as his running mate comes after days of debate over the radicalism and vacuousness of Romney’s tax plan. His proposal won’t say how its deep tax cuts for the rich would be paid for — but if you grant the plan the most generous possible assumptions, the Tax Policy Center found, those tax cuts would have to be paid for by increasing the tax burden on the middle class.

Similarly, as experts have pointed out, Paul Ryan’s infamous budget — which is now officially the overarching blueprint for the whole GOP agenda — simply doesn’t add up unless you presume extraordinarily deep cuts to the nation’s safety net and a shockingly dramatic shrinking of government, even as it, too, cuts taxes deeply on the rich. Those experts see Ryan’s vision as deeply radical. As Robert Greenstein of the Center on Budget and Policy Priorities recently put it, Ryan’s blueprint “would likely produce the largest redistribution of income from the bottom to the top in modern U.S. history.” Greenstein added that “for most of the past half-century,” the Ryan agenda “would have been outside the bounds of mainstream discussion.”

It is now the central, driving idea for the GOP ticket for the presidency of the United States.

In picking Ryan, Romney is confirming his commitment to full-flown economic radicalism — something that he had kept well disguised until the Tax Policy Center study unmasked it. The central idea driving the GOP ticket is not just that tax hikes on the rich must be avoided at all costs. It’s that dramatically reducing the tax burden on the wealthy — coupled with deep cuts to social programs and a quasi-voucherizing of Medicare — is the route back to prosperity.

Call it the “Ryan/Romney vision.” Not the “Romney/Ryan vision.” The “Ryan/Romney vision.” The Ryan pick was urged upon Romney by conservatives who wanted him to “go bold,” i.e., to confirm beyond doubt that he will govern from the Ryan blueprint. “We want the Ryan budget,” Grover Norquist said recently, adding that the paramount requirement in the next president is that he have “enough working digits to handle a pen” to sign it. The Ryan pick is a triumph for this wing of the party.

After all, we already know Romney has the skills to handle a pen. He is now confirming what he intends to sign with it.

The Ryan pick is also a break with Romney’s previous theory of the race. He had previously intended to make the campaign about nothing more than a referendum on the economy and Obama’s stewardship of it. Now it will be a choice between two starkly different ideological visions, one that drags the race onto the turf of tax fairness and entitlements — which is much more in line with the debate Dems wanted.

The press is already accurately framing the pick as a clash of visions. But what’s more important is that Ryan’s vision remains vague. We still don’t know in any meaningful detail how he would achieve the deep cuts necessary to make that vision work.

Which raises a question: How aggressively will the news media scrutinize the true substantive nature of his vision? The press has done a great job pinning Romney down on the real implications of his tax plan, largely thanks to that unsparing Tax Policy Center study. Ryan, by contrast, has been widely accorded the presumption of fiscal “seriousness," mainly because he looks so earnest and genuinely despairing in those videos that show him stalking the halls of Congress in the grip of existential deficit angst.

But now that he is the vice presidential pick — confirming that his worldview will be the one that animates the approach to governing the GOP presidential ticket would adopt — here’s hoping the press gets equally serious about pinning down the true implications of his vision, too.

After all, the entire premise of the Ryan pick is that it is supposed to show how deadly serious the Republican ticket is about getting our fiscal problems under control. Indeed, in his announcement speech, Ryan is supposed to say this: “We won’t duck the tough issues…we will lead!” It’s time to pin Ryan down on what he means by “lead,” and to explain it as clearly as possible to the American people. And if Ryan won’t meaningfullly tell us what he means by it, we need to say so.


UPDATE: As Evan McMorris Santoro points out, the Romney campaign is already distributing talking points claiming the pick doesn’t mean he is embracing the Ryan plan; he vows to release his own plan for the deficit. But Romney has to say this, to avoid looking weak. He has embraced the general principles Ryan espouses time and again, and one assumes there will be heavy conservative pressure on him to hew closely to them as he releases his “own plan.”